The 1983 US Festival, held last May at Glen Helen Regional Park in San Bernardino County, California, may not have drawn the largest outdoor festival crowd ever assembled, but those persons in attendance did witness one of the planet’s most massive outdoor concert sound systems ever pieced together.

Staged over the Memorial Day weekend in a 54-acre bowl scraped out of a hillside in the Los Angeles-area public facility, the US Festival had an $18 million budget, which contained ample resources for the best in sound,lighting and staging. The Festival was produced by the UNUSON Corporation (An acronym for “Unite Us In Song”), which in turn had been set up by Steve Wozniak, the multimillionaire inventor of the Apple personal computer.

Wozniak explains his criteria for choosing a Clair/Showco combination to handle sound for the Festival: “No compromise .. . period! That was it. We shopped around until we found someone who could give us exactly what we wanted without trying to change things, and who was willing to work with us. And that’s what we got. This is essentially the same system which we used for last year’s ‘US 82’ Festival, but I understand that there have been some technical improvements.”

An outdoor site such as the one prepared for the US Festival presents a sound system designer with some very real problems to solve. Outdoor sound requirements for crowds numbering up to 300,000 people are very different from a typical arena tour. One problem in an arena so vast as the US Festival’s 54-acre site is the speed of sound. Since sound waves do not travel quickly enough to provide simultaneous delivery of the music at both the front and rear of the audience area, a series of speaker towers that receive a delayed signal is necessary.

Temperature gradients present a problem of a different sort: since the speaker scaffolding is stacked up into the air, sound waves encounter layers of warm and cool air.The various alternating (and constantly shifting) layers in the atmosphere cause changes in the system’s frequency response.Typically, those loudspeaker units at the top of the stacks will require a more pronounced emphasizing of low and high frequencies

All of which presents the need for a far greater amount of control over the system’s equalization than would normally be the case in a smaller, indoor system.

Figure 1: Clair house system comprised I80 S·4 cabinets and 32 long-throw constant-coverage long-throw horns: 5·4s were stacked I 0 wide and three high on three tiers per side. (click to enlarge)

Clair House System
Main house speaker stacks for the US Festival were provided by Clair Brothers Audio, of Lititz, PA. Situated on sound wings which were 184 feet wide, the entire stage platform from side to side totaled 436 feet - the Clair house system comprised 180 S-4 speaker cabinets stacked 10 wide and three high, in three different tiers on each side of the stage (Figure 1). Additionally, a fourth upper tier of scaffolding was added that contained 32 long-throw high-frequency horns per side .

Roy Clair explains how the US Festival system was assembled, and details some of his philosophy for outdoor speaker systems: “This year, we were quite lucky. A lot of our tours ended, which gave us a lot of available gear during this time frame. I can’t say that we planned it this way, because you certainly can’t go around telling your accounts when to go on the road, but it did work out well.

“We already had several truckloads of gear here on the West Coast, which logistically worked out for us. Last year, we scheduled [the Festival] as best we could, and we got help from other people. This year, we did not have to farm out any parts of the system, although we do have Showco providing the delay towers again.

1983 US Festival arena and stage layout. (click to enlarge)

“Last year, Clair had quite an advantage during the bidding, politically speaking, since a majority of the acts on the bill were our touring accounts already. 80 these acts requested that Wozniak use Clair. We are here again this year primarily because everything worked out so well last time.”

According to Clair, the US Festival tied up sound equipment for more than three weeks, although the Festival involved only four days of actual live music. “The time involved for transportation, the week of setup time and system testing, plus the four-day break between the rock and the country performance days, really stretched it out,” he says.“We have many members of our staff who have been working on just this project for more than a month.

“Our advance-notice time was about three months; then, coordinating the on-site arrival of all of the gear, and assembling four or five different road systems into a single large cohesive system, was the big job.”

Design of the system was done by Clair Bros. after UNUSON informed the company of the basic parameters: crowd size; budget; and site dimensions. “Our cabinets are such that the more of them you stack, the better they get,” Clair offers. “But, with horn-loaded cabinets, that is not always the case. What we have done here is to create massive line arrays of the same type of component, so that the ‘18s all line up—the horns, and so on. The composite boxes are like building blocks; they make it very easy to assemble a large system.”

S-4 Speaker Cabinets
Since 1971, Clair has been building and using the composite loudspeaker cabinet known as the S-4. This cabinet was considered by many to be unique for its time, and still is the standard by which other composite units are judged. More than just a new packaging concept, the S·4 was engineered to break the concert sound system down into “modular” units; one speaker cabinet contained all of the components that would be found in the entire sound system.

The S-4 is a four-way enclosure, containing two 18·inch cone drivers in the low-frequency section; four cone drivers in the mid-bass region; two compression drivers mounted on horns in the midrange section; and compression-type HF units on the top end. Type of speakers used varies from cabinet to cabinet, and five or six different variations of the S·4 have been produced in the past 12 years. However, the basic design has remained constant.

Figure 2: Transducer alignment of Clair S-4 cabinet, shown left on the US Festival stage and right to illustrate driver configuration. (click to enlarge)

“We were really pioneering a new concept when we first assembled the S·4s,” Clair concedes. “We wanted something that would pack well in the trucks, that could be easily handled, that looked clean, and would give all of our systems a consistent sound. We are constantly trying new transducers, new horn designs, but I think the all-in-one box has proven itself to be the most efficient way to carry a concert system from city to city,”

The S-4 weighs approximately 425 pounds fully loaded, and measures 43 by 45 by 22 inches deep. Each type of speaker component within the cabinet is grouped in such a way as to create line arrays when the cabinets are stacked (Figure 2).

Each of the three tiers of S·4 cabinets on each sound wing was split into two, separately-controlled systems: half were pointed straight ahead; and the remaining half on each level were given a gentle hemispherical curve to the outside, such that the outermost cabinets in each stack were angled away from the inside cabinets at approximately 45 degrees (Figure 3). According to Clair, each half of each tier had separate crossover feeds, and the input signal to each crossover was processed through the company’s own third-octave equalizer.

With each side having four tiers, this gave the Clair engineers eight different sets of crossover and equalization controls on each side. (The left stack, for example, was split into eight banks of speaker cabinets, with one output mix going to eight sets of system output electronics.)

Figure 3: Speaker cabinets were laid out in a gentle curve so that the outside of each stack angled away from the straight-ahead stacks by 45 degrees. Note cone drivers in vertical line array. (click to enlarge)

“We found it to be really important that the engineers have complete control over what was coming out of such a large loudspeaker array,” relates Clair. “With this set-up, the lowest tier can have its level attenuated greatly so as to not harm the ears of the ground-level crowd. The middle tiers can be adjusted as needed to provide more or less of a given frequency range. And the top tier can be set to throw the sound all the way back to the rear of the site.”

System specifications for the US Festival called for 90 to 100 dB average sound pressure level of program material at the rear concession-stand area- - a distance of nearly a quarter-mile.